The database from the testing of approximately 1200 chemicals for mutagenicity in Salmonella is being analyzed. Approximately 250 of these chemicals have also been tested for carcinogenicity by the NCI/NTP. There are also a large number of chemicals that have also been tested for their ability to mutate mouse lymphoma (L5178Y) cells, or produce chromosome damage in cultured Chinese hamster ovary (CHO) cells. The correlations between Salmonella mutagenicity and carcinogenicity are being analyzed, as well as the correlations between Salmonella mutagenicity and the responses in mammalian cells. A mutagenic response in Salmonella is highly predictive of carcinogenicity, whereas a negative response is not predictive of noncarcinogenicity. The correlation achieved between mutagenicity and carcinogenicity is highly dependent on the class of chemical examined. The other in vitro test systems, when used in concert with, or subsequent to Salmonella, do not appear to significantly enhance the predictivity.